Portable communications devices such as mobile telephones typically operate with a limited power supply in the form of a battery, and hence have a limited period of operation before the battery must be recharged or replaced.
Many efforts are being made to reduce the power consumption of such portable devices, in order to lengthen the above period of operation. When such a portable device is not actively involved in a call, (a so-called standby mode), the device periodically `listens` to a control channel, which will then alert the device in the case of an incoming call. This is referred to as Discontinuous Receiving Mode (DRX mode). During DRX mode, most power is consumed when the receiver apparatus is actually switched on, and therefore a key goal is to reduce the receiver apparatus `on` time.
A problem with the receiver apparatus is that whilst receiving and demodulating a signal, Direct Current (DC) interference generated internally interferes with the signal, limiting dynamic range.
A known solution to this problem is to provide in the receiver apparatus, a DC adapt step, prior to demodulating the signal, which substantially cancels the DC interference. However the receiver apparatus must be switched on during this DC adapt step, thereby causing an increased `on` time of the receiver apparatus and hence resulting in a large power drain.
This invention seeks to provide a demodulation method which mitigates the above mentioned disadvantages.